1. Field of the Invention
The present invention relates to a sheet feeding device and an image forming apparatus having the sheet feeding device for separating a sheet from a plurality of stacked sheets and feeding each separated sheet.
2. Description of the Related Art
In an image forming apparatus such as a printer and a copier, a sheet feeding device has been used to separate a sheet from sheets stacked on a sheet stacking portion and feeding each separated sheet. Recently, in order to convey sheets at a high rate in the above sheet feeding device, a so-called air sheet feeding device has been suggested. In the air sheet feeding device, a fan is actuated to blow gas (mainly air) to the side face at the upper portion of the sheets stacked on a sheet stacking portion, so that multiple sheets at the topside of the stacked sheets are blown up. At this occasion, the topmost sheet is sucked to and fed by a conveyance belt (see U.S. Pat. No. 5,645,274).
In the air sheet feeding device, an auxiliary separation fan has been suggested to be attached to a side-end restricting plate for restricting the side end of stacked sheets, so that air is blown from an opening arranged on the side-end restricting plate. With this structure, sheets are blown up and separated more reliably (see Japanese Patent Application Laid-Open No. 2003-182873).
There exists an air sheet feeding device having a forward conveyance roller arranged on the upstream side of the suction/feeding mechanism, so that a sheet is fed by this forward conveyance roller and is thereafter sucked to and fed by the conveyance belt (see Japanese Patent Laid-Open No. 2005-179043).
In a recent image forming apparatus, sheets are fed at a high rate, and accordingly, a sheet feeding device often employs the above air sheet feeding method. However, as the apparatus is used in various environments and various sheet materials are used, a so-called multi-feeding (two or more sheets are fed at a time) is likely to occur.